As far as I'm aware, I do not believe these are meant to be taken apart thus, you will not be able to roll opamps. Tbh, I don't you can roll opamps even if you do open it up as it's a pretty simple dac amp combo, but don't quote me on that.

I'm currently using a Lexicon Alpha for its DAC/Headphone amp with my Sony MDR-V6 headphones.
Would I benefit or notice any improvement in using the NuForce UDac-3?
From what I can find the specs of the Alpha: 24bit D/A
Headphone Output: 20 mW per channel at 50 Ohms

I have Philips shp9500, and I use it for gaming mostly, and it's really good. I wanted to try using it with an amp/dac combo to see if it's worth the try. Any suggestions? Also I'm really noob in the audiophile area. :P

You may see some improvement if the sound card in your Laptop is bad by replacing it with a DAC, but the EDC3 probably won't sound much different with an amp. They are very sensitive IEMs (100 dB at 1 kHZ) with low impedance (16 ohm) which means they're generally made to be used and without an amp, which again should generally mean they sound good (and reach a loud enough volume) without one.

I'm pretty sure it will, I'm currently running the T2 from a similarly-priced dac/amp combo (Hifime Sabre 9018) and it works like a charm, adding a bit more soundstage, cleaner background and more dynamic range compared to the standard headphone out.

I don't think so, even without looking at the charts I'm pretty sure you won't notice big differences between those two. If you wanna improve while keeping it really portable, something like the Audioquest Dragonfly Red seems the way to go.

Would the unit be powered up if I link it up to my phone (Samsung S8) via USB?
I want to use this as a DAC/preamp exclusively for my phone and to my audio gd R28 via RCA when I don't want to switch on my PC.

Personally I've only had Google Pixel and I was unable to get it to work on my phone. HOWEVER the power draw is fairly high on this unit so even if you were to do it this way it will quickly drain all your phone battery.
So I don't recommend this units for your intended purpose, you should probably get something that has either battery or dedicated power such as SMSL M3, Schiit Fulla or portable ones like Oppo HA-2 SE, Chord Mojo.......etc.

If no one responded: Samsung S8 discharge through USB Type-C is limited to 500 mAh at less than 3 V if I am correct. This could change depending on what's connected, but it will never exceed or meet the battery's current Voltage output (usually around 4.1 V) nor over 1500 mAh of total battery discharge.
A typical S8, S8+, and Note8's discharge is 550 mAh idle with the screen off and the usual amount of background apps, and upwards of 850 mAh during usage.

The only complaint is that the material quality seems to be usb port, bursting and breaking told. If it's cheap enough for me, it looks like I can not throw away my money. We expect better price performance products.
Despite the price I did not like

Yes I it does have a few output options straight from the DAC BUT if you bought the Alex Cavali amp I'd really spend a little bit more and pair it with a nicer DAC lol.
Something along the line of Massdrop SDAC or ODAC or JDS OL DAC or Schiit Modi 2 would be more comparable.
EDIT: Ops just realize the message was from 6 weeks ago hopefully you got something already LOL.

It's a good amp to start with. It isn't the best for efficient headphones or sensitive IEMs due to the higher impedance out, but I didn't notice anything too strange with the Fostex Purplehearts or Ebony, and those are more sensitive than the typical 32-80 ohm headphones.
You aren't going to crank 300-600 ohm headphones to ear bleeding levels with it, but it will power them just fine.
The only things at this price point with a little more power will be a Magni 3 or the Xduoo Ta-10, and even then it's only 500mW more at max, so any of those are good starters.
The D30 is one of my favorite DACs, and the SMSL SU-8 that is dropping again is the least expensive DAC I've seen with balanced ins and outs if you plan on going that route in the future. I have both and they are great. Don't worry about any DACs more exppensive than those until you start getting amps that are getting closer to the $1k mark, as the benefits to a more expensive DAC aren't as great as headphones first and amp second, DAC third.